1. Field of the Invention
The present invention relates to an ink-jet printing method and an ink-jet printing apparatus, and particularly to an ink-jet printing method and an ink-jet printing apparatus for printing by the use of treating liquid which insolubilizes a coloring material in an ink. An ink-jet printing method and an ink-jet printing apparatus according to the present invention are applicable to equipment for printing characters, images or the like on a recording medium such as paper, such as a printer, a copying machine and a facsimile machine, and are used in these items of equipment as a printing mechanism.
2. Related Background Art
Treating liquid for insolubilizing a coloring material such as a dye or a pigment in an ink is generally used to improve the water fastness of printed images or the like. The present applicant, however, has focused attention on the fact that the treating liquid significantly affects not only the improvement of such water fastness, but also printability such as density (for example, optical density (OD)) of printed images, sharpness of a printed image edge portion and fixing ability, and has made various proposals.
There has been made, for example, a proposal in which ink dots are formed with a goal of improved OD value by the use of ink using pigment as coloring material, and by use of a treating liquid and by mixing the ink and the treating liquid on a recording sheet.
The combination of ink using the pigment as coloring material and the treating liquid is also preferable to form dots having a so-called sharp boundary, which hardly causes any blurred contours to dots to be formed, in addition to the improved OD.
As described above, printing using the combination of the ink using a pigment as coloring material and the treating liquid is capable of implementing high OD and high sharpness in the image edge portion, thus enabling unprecedented, high-quality printing. The ink-jet printing system, however, leaves room for improvement in terms of the fixing ability to improve the printability.
In a case where, for example, a number of sheets of printing paper are continuously printed, a number of sheets of printing paper discharged after printing will be sequentially stacked. In this case, if fixing of the ink onto the printing paper, that is, the penetration of the ink into the printing paper is insufficient, the ink remains on the surface of the printing paper, the remaining Ink will be transferred onto another sheet of printing paper to contaminate the printing paper. If the ink fixing rate is slow in this manner irrespective of the capacity of the printing head and the printing paper conveying system, it is necessary to make the rate of the discharged sheet itself slower in order to prevent the printing paper from being contaminated thereby. Therefore, the fixing ability in the ink-jet printing-system becomes a comparatively great cause for restraining the number of sheets of printing paper to be outputted per unit time.
On the other hand, as an attempt to improve such fixing ability, there is known a method of using an ink having a high penetrability irrespective of whether or not the treating liquid is used. However, as the printing result using such ink, the OD is low, and the sharpness of the image to be printed is not so excellent.
There is also known a printing method, in which treating liquid having high penetrability and ink using dye as coloring material are used, the treating liquid is first imparted to the printing paper, and the ink is superposedly imparted thereon to thereby insolubilize the dye in the ink. Although, however, the fixing ability is improved by the use of the treating liquid having high penetrability, the OD is low and the sharpness of the image edge is also inferior. This tendency is particularly noticeable when so-called plain paper, which is mostly used for ink-jet printing, is printed.
Even if the treating liquid is used in combination with ink in order to print an image having a high OD and an excellent sharpness as described above, there is the problem that it is difficult to make the printability and the fixing ability compatible. Further, when this fixing ability, that is, penetrability is taken into consideration, there derives a problem of so-called strike-through property in which, in a case where the penetrability is simply enhanced, the coloring material penetrates deeply enough to be able to observe the printed image from the back side of the printed paper, and therefore, it is not an easy technical problem to make the OD or the like and the fixing ability compatible.
The present invention is achieved to solve such technical problems, and is aimed to provide an ink-jet printing method and an ink-jet printing apparatus capable of performing printing having unprecedented, high-level fixing ability while maintaining the OD and sharpness in the image edge portion at high levels, and further capable of effectively restraining the strike-through problem.
It is particularly an object of the present invention to provide an ink-jet printing method and an ink-jet printing apparatus capable of always showing the fixing ability of a fixed level or higher on various types of plain paper. In this respect, the xe2x80x9cplain paperxe2x80x9d here means printing paper generally for use In printers, electrophotographic systems or the like.
Also, other objects of the present invention become apparent also from the following description in the specification.
Therefore, according to the present invention, there is provided an ink-jet printing method comprising the steps of penetrating a treating liquid which contains a component to react chemically with a pigment in an ink and has a penetrability onto a surface layer of a printing medium, and impacting ink-droplets containing the pigment to a portion, among a whole surface of the printing medium, where the treating liquid has been imparted, wherein a penetrating depth of the. pigment applied to the treating liquid on the surface layer of the printing medium is deeper than a penetrating depth of the pigment alone applied to the printing medium on which no treating liquid is imparted and is shallower than a penetrating depth of the treating liquid.
Also, there is provided an ink-jet printing method comprising the steps of forming an ink-receiving part on a surface layer of a printing medium and conducting printing by depositing an ink so as to contact with the ink-receiving part, wherein the ink-receiving part is formed by depositing to a surface of the printing medium a treating liquid comprising a penetrating agent and an insolubilizer to a coloring material in the ink, the ink comprises a predetermined amount of a pigment as the coloring material, an average liquid thickness per pixel of the treating liquid forming the ink-receiving part at the impact on the printing medium is not more than 10 xcexcm, a volume of the treating liquid to a volume of the ink per pixel is not less than xe2x85x9, and an average liquid thickness of the ink per pixel at the impact on the printing medium is from 8 xcexcm to 20 xcexcm.
Further, there is provided an ink-jet printing apparatus to conduct printing by forming an ink-receiving part on a surface layer of a printing medium and then depositing an ink so as to contact with the ink-receiving part, wherein the ink-receiving part is formed by depositing to a surface of the printing medium a treating liquid comprising a penetrating agent and an insolubilizer to a coloring material in the ink, the ink comprises a predetermined amount of a pigment as the coloring material, an average liquid thickness per pixel of the treating liquid forming the ink-receiving part at the impact on the printing medium is not more than 10 xcexcm, a volume of the treating liquid to a volume of the ink per pixel is not less than xe2x85x9, and an average liquid thickness of the ink per pixel at the impact on the printing medium is from 8 xcexcm to 20 xcexcm
Also, according to the present invention, there is provided an ink-jet printing method comprising the steps of applying an ink comprising a pigment in a dispersed state to at least a part of a predetermined region of a printing medium, to which a liquid, which contains a component having a reactivity to the pigment contained in the ink and shows a higher level of penetrability than that of the ink to the printing medium, has been imparted and forming a pigmented portion on the printing medium, wherein a penetrating depth of the pigment applied to the printing medium at the pigmented portion is deeper than a penetrating depth of the pigment at the pigmented portion obtained in a case that only the ink is applied to the printing medium and is shallower than at a tip of penetration of the treating liquid.
Also, according to the present invention, there is provided a printed article having a pigmented portion formed by contacting an ink comprising a pigment in a dispersed state with a liquid, which contains a component having a reactivity to the pigment contained in the ink and shows a higher level of penetrability than that of the ink to the printing medium, and which has been imparted, to the recording medium wherein a penetrating depth of the pigment applied to the printing medium at the pigmented portion is deeper than a penetrating depth of the pigment at the pigmented portion obtained in a case that only the ink is applied to the printing medium and is shallower than at a tip of penetration of the treating liquid.
With this configuration, the ink-receiving part is formed on the surface layer of the printing paper by the treating liquid. More specifically, the treating liquid deposited to the printing medium makes a compatibility-imparting treatment to the surface layer of the paper. That is, this formation promotes penetration of the ink, which next comes into contact with this portion for depositing, into the printing medium.
Also, the treating liquid contains a component (ink insolubilizer), which chemically reacts with a pigment contained in the ink, and is adsorbed on the surface of fiber and/or between the fibers of the printing medium in an ink-receiving part. Thus, the coloring material in the ink is adsorbed. This coloring material contains a predetermined amount or more of pigment, and the pigment particles are adsorbed in the surface layer portion of the paper containing the ink-receiving part.
As a result, the depth of penetration, into the printing medium of the pigment in the pigmented portion to be formed on the paper surface layer portion becomes deeper than that of the pigment in the pigmented portion to be formed when only the ink is imparted to the printing medium, and therefore, the fixing ability is to be improved. On the other hand, since the mobility of the pigment is degraded because of a reaction of the reaction component in the treating liquid with the pigment, the depth of penetration of the pigment can be made shallower than at the tip end of penetration, in the printing medium, of solvent for the treating liquid. As a result, it becomes possible to retain the pigment in the surface layer portion of the printing medium, and a pigmented portion having sufficient optical density can be obtained while the fixing ability of the pigment ink is being improved.
The treating liquid for forming the ink-receiving part impacts on paper as a liquid droplet, and the thickness of the liquid droplet at the impact on the paper is preferably set to 5 to 10 xcexcm. This is because, since the void rate of the printed paper is about 50%, the treating liquid having penetrability instantaneously penetrates to at least a depth of from 10 xcexcm to 20 xcexcm. This thickness affects the fixing ability, OD, the strike-through property or the like of a subsequent ink to be deposited.
That is, since there is a correlation between the thickness of the ink-receiving part and the ink-receiving tolerance, the ink for that amount instantaneously penetrates into the ink-receiving part in the printed paper.
Also, although this ink-receiving part is not always necessary to be uniform on the surface of the printing medium, but may be mottled, it is at least necessary to bring the ink-receiving part into contact with ink droplets corresponding to the pixels on the surface of the paper. More specifically, the ink droplets come into contact with the ink-receiving part, whereby penetration of the ink, reaction of coloring material containing pigment, and diffusion of ink droplets on the surface of the printing medium become possible.
In the course of the process in which the ink penetrates into the ink-receiving part, the pigment in the coloring material is trapped by fiber on which ink insolubilizer has deposited, and when ink of receiving tolerance or more is deposited, the penetration rate lowers, and therefore, the fixing ability is degraded. On the other hand, when the thickness of the ink-receiving part is too large, fine particles in the coloring material in the ink penetrate more deeply, and therefore, the strike-through property is degraded although the fixing ability is improved.
As regards OD, it is known that it can be determined by reflected light up to about 20 xcexcm from the surface of the printing medium, and for this reason, in order to improve the OD, the coloring material in the ink can be densely trapped up to about 20 xcexcm of the surface layer of the printed paper, and an ink-receiving part enough to penetrate the ink for that amount at high rate is formed.
Since the wettability of the ink-receiving part has become high, when the ink comes into contact with the portion and is deposited, the ink instantaneously spreads in the horizontal direction and then high area factor can be secured by a small amount of ink. As a result, strike-through is also reduced.
Also, since the coloring material containing pigment particles is trapped by the insolubilizer in the paper while the ink droplets deposited instantaneously spread on the surface of the printed paper, blurring of the ink such as so-called feathering is greatly reduced, resulting in sharp image edges.
A described above, high fixing ability, high OD, sharp edges and excellent strike-through property can be implemented.